1. Field of the Invention
The present invention relates generally to medical tables for medical procedures, and, in particular, relates to tables that are used for vascular and interventional medical procedures, and, in greater particularity, relates to tables having an iso-axis.
2. Description of the Prior Art
Imaging devices are an important part of medical technology because they provide a view of internal features whether of tissues, bones, or organs. Due to improvements in electronics, imaging devices have become portable, smaller and can be mounted on movable arms with a mobile base. The portable imaging system is used with a mobile table positioned to allow the x-ray source and detector free movement around and about the patient. During a radiology procedure involving x-rays, an iso-center is defined as an orbital center or the point where the x-ray source and detector rotate about. An object of anatomical interest positioned at the iso-center will remain within the field of view as the imaging system is rotated and re-positioned about the patient. It is thus very important and beneficial to position the region of interest within a patient at such a point during the procedure. In some procedures the tabletop must be rotated to provide better access to the patient anatomy. If the region of interest is placed on the imaging iso-center and the table can provide iso-centric rotation the imaging systems and/or the table can be rotated without having the region of interest move outside the imaging area.
The tabletop holding the patient for such procedures thus must be moved if additional areas are to be observed. Many of the tables used for these procedures have tabletops that can be moved in many degrees of freedom. Existing tables typically have a point of rotation that is located under the tabletop; thus as the tabletop is rotated the tabletop is displaced left or right as it swings about an arc with a center of rotation located under the tabletop and patient. During imaging, if the tabletop is rolled to the left or right a region of interest within the anatomy of a patient will appear to move laterally across the field of view of the imaging system. If the center or axis of rotation could be displaced from a location under the table to a point above it then the table axis of rotation could be placed in a location that would be of benefit relative to the position of key parts of the human anatomy; the spine for example as well as simultaneously coincident with the axis of rotation of the imaging system. If the table axis of rotation is placed on iso-center along with the region of interest (a section of the spine) then table rotation can be accomplished without causing the region of interest to drift or move out of the field of view.
There are some table designs that utilize complex linkages and mechanisms to create an approximation of an axis of rotation that is located above the tabletop. In such designs the point of rotation is not fixed though it does exist above the tabletop and within a patient's anatomy.
The manufacturing of these tables thus should minimize complex mechanical devices providing these many degrees of freedom to reduce the cost of these tables.
Examples of tables are shown in several patents and patent application publications. U.S. Patent Application 2003/0145383 discloses a lateral tilting device using four legs driven by a motorized screw. The top of the legs are attached to the tabletop and the bottom to the support column. U.S. Patent Application 2004/0172758 discloses a table having longitudinal tilt with the ability to provide iso-center tracking. The iso-center being a point at which radiation is provided to the patient by the radiating machine. U.S. Patent Application 2005/0015878 discloses a lateral and longitudinal tilting device. A frame is mounted to a support column. The frame is pivoted on orthogonal axes having two actuators driving the respective frame. The axes of rotation are thus below the tabletop. U.S. Pat. No. 6,094,760 discloses a table having a lateral tilting device. The tabletop has a pair of circular tracks that travel upon rolls thereunder. A driving means is attached to an axle under the tabletop. U.S. Pat. No. 6,681,423 discloses a table with lateral tilt using four legs between a top and bottom frame. A pair of actuators controls the movement of the top frame. U.S. Pat. No. 7,000,271 discloses a C-arm x-ray machine providing x-rays to an iso-center point.
Accordingly, there is a need for an imaging table having an iso-roll axis above the tabletop and located on or substantially close to the iso-center of the imaging system.